Note: Descriptions are shown in the official language in which they were submitted.
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FLUOROELASTOMER COMPOSITION FOR COLD SHRINK ARTICLES
FIELD
The present invention relates generally to compositions for cold shrinkable
articles
for use in various applications. In particular, the present invention relates
to compositions
for cold shrinkable articles formed from a composition including a
fluoroelastomer.
BACKGROUND
Cold shrinkable articles are used in a variety of different applications such
as, for
example, splicing together lengths of wire or cable and protecting, sealing,
and/or
insulating substrates from adverse environmental conditions. Examples of
industries that
use cold shrinkable articles include the automobile, aerospace, power,
telecommunication,
chemical, and defense industries.
It is known to form cold shrinkable articles from elastomeric compositions
that
include an elastomer to facilitate expansion and contraction of the article.
Examples of
known elastomers employed in cold shrinkable articles include EPDM rubber or
silicone
rubber. A problem in the art has been producing compositions that maintain
desirable
elongation-at-break and desirable permanent set properties in high temperature
conditions.
SUMMARY OF THE INVENTION
Embodiments of the invention include a composition that achieves desirable
elongation-at-break and desirable permanent set properties in high temperature
conditions.
For example, embodiments can include an elastomeric composition including a
fluoroelastomer composition, where the elastomeric composition is
substantially free of an
epichlorohydrin composition. Also, for example, embodiments can include a
filler
material. The filler material can include, for example, a reinforcing-grade
carbon black
and a silica. Also, for example, embodiments can include a peroxide curative.
For example, embodiment can include a method of use. Embodiments of the
method can include providing an elastomeric composition including a
fluoroelastomer
composition, where the elastomeric composition is substantially free of an
epichlorohydrin
composition. Embodiments can also include providing a filler material
including a
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reinforcement-grade carbon black. Embodiments can also include providing a
peroxide
curative. Embodiments can also include mixing the elastomeric composition, the
filler
material, and the peroxide curative to form a blend composition. Embodiments
can also
include curing the blend composition to form a tubular cold shrinkable
material.
Embodiments can also include installing a removable core inside the tubular
cold shrinkable
material to support the cold shrinkable material in an expanded state.
According to one aspect of the present invention, there is provided an
elastomeric composition comprising: a fluoroelastomer; a filler material, the
filler material
comprising one or both of a silica and a reinforcement-grade carbon black
having an average
particle size by less than about 40 nm; and a peroxide curative wherein the
quantity of one or
both of the silica and the reinforcement-grade carbon black and silica is in
the range of about
10 phr to about 25 phr, and the quantity of peroxide curative is in the range
of about 1 phr to
about 6 phr; the elastomeric composition being substantially free of an
epichlorohydrin.
According to another aspect of the present invention, there is provided a
method for making a cold shrink article comprising: (a) providing an
elastomeric composition,
the elastomeric composition comprising: a fluoroelastomer; a filler material,
the filler
material comprising one or both of a silicia and a reinforcement-grade carbon
black having an
average particle size of less than 40 nm; and a peroxide curative; wherein the
quantity of one
or both of the reinforcement-grade carbon black and the silica is in the range
of about 10 phr
to about 25 phr, the quantity of peroxide curative is in the range of about 1
phr to about 6 phr,
and the elastomeric composition is substantially free of epichlorohydrin; (b)
mixing the
components of the elastomeric composition to form a blend composition; and (c)
curing the
blend composition to form a tubular cold shrinkable material; and (d)
installing a removable
core inside the tubular cold shrinkable material to support the tubular cold
shrinkable material
in an expanded state.
According to still another aspect of the present invention, there is provided
an
article of manufacture comprising: a tubular cold shrinkable material
comprising a reaction
product of the composition as defined herein.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a cold shrinkable article of the present
invention in
a relaxed state, prior to expansion.
FIG. 2 is a perspective view of the cold shrinkable article of FIG. 1 in an
expanded
state on a core.
FIG. 3 is a perspective view of the cold shrinkable article of FIG. 1 in an
expanded
state on the core of FIG. 2, with an associated substrate.
FIG. 4 is a perspective view of the cold shrinkable article of FIG. 1
partially
located on the core of FIG. 2 and partially deployed on the substrate of FIG.
3.
FIG. 5 is a perspective view of the cold shrinkable article of FIG. 1
including
indicia and fully deployed on the substrate of FIG. 3.
FIG. 6 is a perspective view of a branched cold shrinkable article of the
present
invention in a relaxed state prior to expansion.
FIG. 7 is a perspective view of the branched cold shrinkable article of FIG. 6
in an
= 15 expanded state on a plurality of cores.
FIG. 8 is a perspective view of a corrugated cold shrinkable article of the
present
invention.
DETAILED DESCRIPTION
The present invention relates to an article of manufacture including a tubular
cold
shrinkable material formed from an elastomeric material. The term "cold
shrinkable", as
used herein, is defined as the capability of an article (or a portion of an
article) to *shrink
from an expanded state toward a relaxed or a partially expanded state.
Elastomers can be included in the compositions of cold shrinkable articles to
allow
the cold shrinkable articles to expand from a relaxed state to an expanded
state, while also
allowing the articles to cold shrink back toward the relaxed state. In
embodiments of the
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invention, for example, the elastomeric composition can include a
fluoroelastomer
composition, and the elastomeric composition can be free from any
epichlorohydrin
composition.
Unless otherwise stated, all concentrations herein are expressed in parts by
weight
per hundred parts by weight rubber (phr), with the rubber defined to be the
total weight of
the fluoroelastomer. Thus, as used herein, the phr of a particular component
represents the
parts by weight of the component relative to 100 total parts by weight of
fluoroelastomer.
Some examples of suitable fluoroelastomers for use in the elastomeric
compositions of the present invention include fluorinated elastomeric
copolymers (i.e.,
polymers derived from two or more different monomers), fluorinated elastomeric
terpolymers (i.e., polymers derived from three different monomers) and
fluorinated
elastomeric polymers including more than three different monomers. Some
examples of
suitable fluorinated elastomeric copolymers include copolymers of vinylidene
fluoride,
tetrafluoroethylene, and hexafluoropropylene (e.g., the DAI-EL G-801 product
and the
DAI-EL G-802 product, both commercially available from Daikin Industries of
Osaka,
Japan) and copolymers of vinylidene fluoride and tetrafluoroethane-
perfluoro(methyl
vinyl ether) (e.g., the VTR 8500 product or VTR 8650 product, both
commercially
available from Dupont-Dow Elastomer of Wilmington, DE). Examples of suitable
fluorinated elastomeric terpolymers include terpolymers of
tetrafluoroethylene,
hexafluoropropylene and vinylidene fluoride. In some embodiments, the
fluoroelastomer
may be modified with iodine or another material to facilitate cross-linking of
the
fluoroelastomer.
Besides fluoroelastomer, the elastomeric compositions of the present invention
may also include additional optional materials such as reinforcement-grade
(reinforcing)
filler materials, fluoroplastics in addition to fluoroelastomers, pigments,
energy-beam
absorbents, antioxidants, stabilizing agents, fillers, oils, processing aids,
neutralizers,
rheology modifiers, silane coupling agents, cross-linking materials (e.g.,
cross-linking
agents, cross-linking co-agents, and cure accelerators), lubricants, flame
retardants, flame
retardant synergists, antimicrobials, any other additive known in the art, and
any
combination of these in any proportion. The concentration of these additional
materials in
the elastomeric composition of the present invention may be any concentration
sufficient
to provide a desired result.
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Reinforcement-grade (reinforcing) filler material may optionally be included
in the
elastomeric composition of the present invention to enhance the split and tear
properties of
cold shrinkable articles (formed from the elastomeric composition) at elevated
temperatures. Examples of suitable filler materials include silica-based
reinforcement
filler, reinforcement-grade carbon black, fluoroplastics, clays, and any
combination of any
of these in any proportions.
As used herein, the term "silica-based reinforcement filler" is defined to
include all
compounds of the formula Si02 (e.g., pure silica); all compositions that
include at least
about ten weight percent of Si02 and/or an Si02 derivative, based upon the
total weight of
the composition; all silicates; and any combination of any of these in any
proportion.
Examples of suitable silica-based reinforcement fillers include silica (also
referred to as
silicon dioxide); silane-treated silica; fumed silica (e.g., such as the
CABOSIL M-5
product commercially from Cabot Corporation of Billerica, MA); silane-treated
fumed
silica such as, for example, the AEROSIL R972 product, the AEROSIL R974
product,
and the AEROSIL 200 product that are all commercially available from Degussa
Company of Parsippany, NJ and the CABOSIL line of silane-treated fumed silica
products commercially from Cabot Corporation of Billerica, MA; silicates; and
any
combination of any of these in any proportion. Examples of suitable silicates
include
calcium silicate, aluminum silicate, and mixtures of these. In some
embodiments, the
average particle size of the silica-based reinforcement filler may be less
than about 30
nanometers (nm). In other embodiments, the average particle size of the silica-
based
reinforcement filler may be as low as about 10 nm and as high as about 20 nm.
The phrase "reinforcement-grade carbon black" as used herein, includes any
carbon black with an average particle size smaller than about 40 nm, which
corresponds to
an average surface area of about 65 m2/g. Some particularly suitable average
particle sizes
for reinforcement-grade carbon black range from about 9 nm to about 40 nm.
Carbon
black that is not reinforcement grade include carbon black with an average
particle size
larger than about 40 nm. As shown in Table 1, some examples of suitable
reinforcement-
grade carbon black include, for example, N-100 series carbon black, N-200
series carbon
black, and N-300 series carbon black, which are all commercially available
from Cabot
Corporation of Billerica, MA.
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TABLE 1
ASTM Particle
= = ¨ =
Name Abbrev. Deal.* _Size
n m
Super Abrasion Furnace SAF N110 20-25
IgAr -026-
-RAr
Channel EPC N300 30-35
-FEr -NSW
-Rmr -WY
rTeliirkeliiraCtrir¨
Furnace SRF N770 70-96
Y NiU -T8'62tid"1
VeZilirTnignia
'18n9P
Elastomers including a filler material of reinforcement-grade carbon black can
offer improved tensile strength, improved modulus, greater stiffness, and
increased
resistance to abrasive wear. On the other hand, elastomers including a carbon
black filler
material that is not reinforcement-grade may not exhibit the enhanced
properties or
characteristics that are exhibited by reinforcement-grade carbon blacks, as
illustrated in
the Examples corresponding to Tables 2-4. Embodiments of the present invention
o demonstrate that reinforcement-grade carbon black offers advantageous
mechanical
properties when utilized with fluoroelastomers at both room temperature and
elevated
temperatures, as illustrated in the Examples corresponding to Tables 2-4.
Examples of fluoroplastics that may serve as (or as part of) the reinforcement-
grade (reinforcing) filler material include homopolymers of
tetrafluoroethylene monomers,
any copolymer that includes a tetrafluoroethylene monomer, any terpolymer that
includes
a tetrafluoroethylene monomer, any other polymer that includes a
tetrafluoroethylene
monomer and three or more different monomers, and any combination of any of
these in
any proportion. Examples of suitable copolymers include copolymers of
tetrafluoroethylene and hexafluoropropylene (e.g., the ZONYLO MP 1500 product
commercially available from DuPont Fluoroproducts of Wilmington, DE).
Examples of suitable clay fillers that may serve as (or as part of) the
reinforcement-grade (reinforcing) filler material include silane-treated
kaolin clay
(aluminum silicate) fillers commercially available from Engelhard Corporation
of Iselin,
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New Jersey under the trade designations "Translink 37", "Translink 77",
"Translink 445",
"Translink 555", and "Translink HF-900".
In some embodiments of the invention, the concentration of the filler material
can
be in the range of about 10 phr to about 25 phr. For example, if the filler
materials include
only a fumed silica, the fumed silica can be in the range of about 10 phr to
about 25 phr.
Also, for example, if the filler materials include only a reinforcement-grade
carbon black,
the reinforcement-grade carbon black can be in the range of about 10 phr to
about 25 phr.
Also, for example, if the filler materials include both a fumed silica and a
reinforcement-
grade carbon black, the concentration of the combination of filler materials
can be in the
range of about 10 phr to about 25 phr.
The elastomeric composition of the cold shrinkable material can also include
an
energy beam absorbent. The energy beam absorbent can provide for an energy
beam
induced indicia charred on an external surface of the cold shrinkable material
responsive
to application of a focused energy beam on the energy beam absorbent. Examples
of
suitable energy beam absorbents for use in the elastomeric compositions of the
present
invention include PolyOne Material No. AD 3000051160 ("Stan-Tone MB-27838
Black"), PolyOne Material Product No. CC10041306WE, and "Stan-Tone MB-29293"
(all available from PolyOne Corporation of Suwanee, Georgia); RTP Material No.
RTP
0299 x 102892 SSL-801191, available from RTP Company of Winona, Minnesota;
Clariant Material No. 00025275, available from Clariant Masterbatches Division
of
Albion, Michigan; Ticona Material No. 1000-2LM ND3650, available from Ticona
of
Summit, New Jersey; BASF Material No. NPP TN020327 ("Ultramid B3K LS Black
23189"), available from BASF Corporation Performance Polymers of Mt. Olive,
New
Jersey; and combinations thereof These energy beam absorbent materials may
include
titanium dioxide, mica, and combinations thereof Titanium dioxide may function
as both
a pigment and an energy beam absorbent, as discussed in Birmingham, Jr. et
al., U.S.
Patent No. 5,560,845.
The elastomeric compositions of the present invention may include a pigment or
combination of pigments to affect a base color of cold shrinkable articles
formed from the
elastomeric compositions of the present invention. Examples of suitable
pigments include
titanium dioxide; carbon black; zinc oxide; pression blue; cadimum sulfide;
iron oxide;
chromates of lead, zinc, barium, and calcium; azo; thioindigo; anthraquinone;
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anthoanthrone; triphenonedioxazine; fat dye pigments; phthalocyanine pigments,
such as
copper phthalocyanine pigment and its derivatives; quinacridon pigment;
pigments
commercially available under the trade designations "Cinquasia", "Cromophtal",
"Filamid", "Filester", "Filofin", "Hornachrome", "Horna Molybdate",
"Hornatherm",
"Irgacolor", "Irgalite", "Irgasperse", "Irgazin", "Micranyl", "Microlen",
"Microlith",
"Microsol", and "Unisperse", all from Ciba Specialty Chemicals of Tarrytown,
NY; and
any combination of any these in any proportion. In some embodiments, the color
and
concentration of pigment(s) incorporated within the elastomeric composition
may depend
upon how much energy beam absorbent is incorporated. As one example, a yellow-
color
pigment may be used in combination with an energy beam absorbent to yield cold
shrinkable articles that, when exposed to a focused energy beam, exhibit high-
contrast
energy-beam induced indicia.
Examples of suitable antioxidants for use in the elastomeric compositions of
the
present invention include solutions of zinc 2-mercaptotoluimidazole in
petroleum process
oil (e.g., "Vanox ZMTI " and "Vanox MTI" commercially available from R.T.
Vanderbilt
Company, Inc. of Norwalk, Connecticut); mixtures of octylated diphenylamines
(e.g.
"Agerite Stalite" commercially available from R.T. Vanderbilt Company, Inc. of
Norwalk,
Connecticut); phenolic-based antioxidants (e.g., IRGANOX 1010 commercially
available
from Ciba Specialty Chemicals); aromatic amine type antioxidants (e.g.,
NAUGARD
445 commercially available from Crompton Corporation of Middlebury,
Connecticut); and
combinations of these.
Examples oils that may suitably be included in elastomeric compositions of the
present invention include hydrocarbon oils (e.g. polychlorotrifluorethylene)
commercially
available from Halocarbon Production Corporation of River Edge, NJ under the
trade
designation Halocarbon 95).
Examples of some suitable cross-linking agents for the elastomeric
compositions
include amines and peroxides, including peroxide curatives, such as the
following
peroxides that are commercially available from R.T. Vanderbilt Company, Inc.
of
Norwalk, Connecticut: dicumyl peroxide (e.g., the VAROX DCP product, the
VAROX
DCP-40C product, the VAROX DCP-40KE product, and the VAROX DCP-40KE-HP
product); benzoyl peroxide (e.g., the VAROX ANS product); dibenzoyl peroxide
(e.g.,
the VAROX A 75 product); 2,5-dimethy1-2,5-di(t-butylperoxy) hexane (e.g., the
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VAROX DBPH product, the VAROX DBPH 40 MB product, the VAROX DBPH-50
product, the VAROX DBPH-50-HP product, the VAROX DBPH-P20 product, and the
VAROX DCP-40KE product); t-butyl perbenzoate (e.g., the VAROX TBPB product
and the VAROX TBPB-50 product); 2,5-dimethy1-2,5-di(t-butylperoxy) hexyne-3
(e.g.,
the VAROX 130 product and the VAROX 130-XL product); alpha, alpha-bis(t-
butylperoxy)diisopropylbenzene (e.g., the VAROX VC-R product); di-(2-tert-
butylperoxyisopropyl) benzene (e.g., the VAROX 802-40C product, the VAROX
802-
40KE product, and the VAROX 802-40KE-HP product); di-(2-tert-
butylperoxyisopropyl) benzene in EPR (e.g., the VAROX 802-40MB product);
io derivatives of any of these; and any combination of these in any
proportion. Examples of
suitable cross-linking agent concentrations in the elastomeric compositions,
such as for
example Varox peroxide curative, range from as low as about 1 phr to as high
as about 6
phr.
Cross-linking co-agents may be incorporated in the elastomeric compositions of
the present invention to enhance the cross-linking reaction. Examples of
suitable cross-
linking co-agents for incorporation in the elastomeric compositions include
triallyl
isocyanurates (e.g., the TAIC DLC-A product commercially available from
Natrochem
Inc. of Savannah, GA.) and acrylic co-agents. Examples of suitable acrylic co-
agents
include multi-functional monomers, such as difunctional and trifunctional
monomers.
Examples of suitable difunctional monomers include the following, which are
commercially available from Sartomer Company, Inc., Exton, Pennsylvania: 1,3-
butylene
glycol diacrylate,1,3-butylene glycol dimethacrylate, 1,4-butanediol
diacrylate, 1,4-
butanediol dimethacrylate, 1,6 hexanediol diacrylate, 1,6 hexanediol
dimethacrylate,
aliphatic dimethacrylate monomer, alkoxylated aliphatic diacrylate,
alkoxylated
cyclohexane dimethanol diacrylate, alkoxylated cyclohexane dimethanol
diacrylate,
alkoxylated cyclohexane dimethanol diacrylate, alkoxylated hexanediol
diacrylate,
alkoxylated hexanediol diacrylate, alkoxylated hexanediol diacrylate,
alkoxylated
neopentyl glycol diacrylate, alkoxylated neopentyl glycol diacrylate, aromatic
dimethacrylate monomer, caprolactione modified neopentylglycol hydroxypivalate
diacrylate, caprolactone modified neopentylglycol hydroxypivalate diacrylate,
cyclohexane dimethanol diacrylate, cyclohexane dimethanol dimethacrylate,
diethylene
glycol diacrylate, diethylene glycol dimethacrylate, dipropylene glycol
diacrylate,
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ethoxylated (10) bisphenol alpha diacrylate, ethoxylated (2) bisphenol alpha
dimethacrylate, ethoxylated (3) bisphenol alpha diacrylate, ethoxylated (30)
bisphenol
alpha diacrylate, ethoxylated (30) bisphenol alpha dimethacrylate, ethoxylated
(4)
bisphenol alpha diacrylate, ethoxylated (4) bisphenol alpha dimethacrylate,
ethoxylated (8)
bisphenol alpha dimethacrylate, ethoxylated bisphenol alpha dimethacrylate,
ethoxylated
bisphenol alpha dimethacrylate, ethoxylated(10) bisphenol dimethacrylate,
ethoxylated(6)
bisphenol alpha dimethacrylate, ethylene glycol dimethacrylate,
hydroxypivalaldehyde
modified trimethylolpropane diacrylate, neopentyl glycol diacrylate, neopentyl
glycol
dimethacrylate, polyethylene glycol (200) diacrylate, polyethylene glycol
(400) diacrylate,
io
polyethylene glycol (400) dimethacrylate, polyethylene glycol (600)
diacrylate,
polyethylene glycol (600) dimethacrylate, polyethylene glycol dimethacrylate,
polypropylene glycol (400) dimethacrylate, propoxylated (2) neopentyl glycol
diacrylate,
tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate,
tricyclodecane
dimethanol diacrylate, triethylene glycol diacrylate, triethylene glycol
dimethacrylate,
tripropylene glycol diacrylate, tripropylene glycol diacrylate, and
combinations thereof.
Examples of suitable trifunctional monomers include trimethylolpropane
trimethacrylate,
trimethyolpropane triacrylate, and combinations thereof Examples of suitable
cross-
linking co-agent concentrations in the elastomeric compositions of the present
invention
range from as low as about 0.5 phr and as high as about 4.5 phr, on a weight
basis.
The elastomeric composition of the cold shrinkable material can be prepared by
blending the components of the elastomeric composition, including the
fluoroelastomer, in
an appropriate mixing apparatus. For example, the components of the
elastomeric
composition may generally be combined in any order in an appropriate mixing
apparatus
at a component temperature of about 60 C.
Additional optional materials may also be included with the fluoroelastomer
prior
to mixing. If cross-linking agents or cross-linking co-agents are to be
incorporated in the
elastomeric composition, the components including the fluorelastomer may be
blended
together in a first mixing step as described above. The cross-linking agents
and/or cross-
linking co-agents may then be blended into the elastomeric composition in a
second
mixing step at a lower temperature than the first mixing temperature, such as
between
about 50 C and about 100 C, to prevent premature cross-linking.
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The elastomeric composition may then be formed into a cold-shrink article by
any
suitable process such as, for example, extrusion or molding. In some
embodiments, the
elastomeric composition of the cold-shrink article is cured, using a suitable
curing process,
to affect cross-linking of the elastomeric composition. Some examples of
suitable curing
processes include, for example, elevated temperature and pressure conditions
(e.g.,
autoclaving), irradiation, or any other suitable curing process known in the
art.
In some embodiments, the cold-shrink article may be autoclaved in an oxygen-
free
and/or water-free atmosphere, with the oxygen-free and/or water-free
atmosphere being
used in place of steam. As used herein, unless otherwise stated, the term
"oxygen-free
atmosphere" refers to an atmosphere of a set volume of gas that includes less
than about
one volume percent oxygen, based on the total volume of the gas in the
atmosphere, and
the term "water-free atmosphere" refers to an atmosphere of a set volume of
gas that
includes less than about 0.1 volume percent water vapor, based on the total
volume of the
gas in the atmosphere. Examples of oxygen free-atmospheres include atmospheres
including greater than about 99% by volume of nitrogen gas, argon gas, helium
gas, xenon
gas, neon gas, any other suitable inert gas, and combinations of any of these
in any
proportion. For example, tubing of the present invention may be autoclave-
cured in a
mold. As used herein, the term "tubing" refers to a hollow cylinder open on
both ends. In
one embodiment, the tubing is first formed (e.g., by extrusion) and then
placed inside
spiral grooves of an aluminum mold. The mold is placed in a heated press and
subjected
to a temperature of about 185 C and a pressure ranging from about 5-14
megapascals
(Mpa) (about 75-200 psi). One end of the tubing is connected to a pressurized
nitrogen
gas supply containing about 99.5% nitrogen gas by volume. The mold may be
purged for
about two minutes with the pressurized nitrogen gas supply at a flow rate of
about 40
cubic ft of the pressurized nitrogen gas. Any other purge time and flow rate
sufficient to
reduce oxygen and/or moisture to acceptable levels may also be used. After the
initial
purging, the mold is sealed off, and the pressure inside the mold may be
maintained at
about 200 pounds per square inch (psi) for about 20 minutes. The mold is then
released
and the pressure in the mold is allowed to return to atmospheric pressure. The
tubing may
then be removed from the mold and cooled.
The elastomeric compositions of the present invention may be formed into cold
shrinkable articles of any shape or geometric configuration known in the art.
Some non-
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exhaustive examples of cold shrinkable articles include tubing, plaques, and
multiple-
branched structures (i.e., tube-like structures with multiple entrances and/or
exits).
Cold shrinkable articles formed from elastomeric compositions of the present
invention may exhibit various advantageous mechanical properties in various
combinations under various environmental conditions (e.g., room temperature or
150 C).
The cold shrinkable material formed from the elastomeric composition exhibit
improved
elongation, permanent set, and tear properties while in expanded states at
elevated
temperatures. Some embodiments of cold shrinkable articles of the present
invention may
be exposed, in an expanded state, to temperatures of at least about 150 C for
an extended
1 o period of time without exhibiting, upon unaided visual inspection by a
human eye, any
splitting, tearing, or breakage.
For example, in some embodiments, a cold shrinkable material can include an
elastomeric composition including a fluoroelastomer, and the fluoroelastomer
is mixed
with a reinforcement-grade carbon black, a fumed silica, and a peroxide
curative. After
the entire processing of the elastomeric article is completed, including the
proper peroxide
curing process, the resultant elastomeric composition can exhibit advantageous
properties,
in particular, for cold shrink materials.
In some embodiments, a proper weight percent of reinforcement-grade carbon
black, fumed silica, and peroxide curative should be maintained to establish
desirable
elongation-at-break properties and desirable permanent set properties even
while
experiencing high temperature conditions. For example, too high a percentage
of peroxide
may result in undesirably high permanent set properties, and too low a
percentage of
peroxide may result in undesirably low elongation properties. Also for
example, too high
a percentage of carbon black and/or silica filler material may result in
undesirably low
elongation properties, and too low a percentage of carbon black and/or silica
filler material
may result in undesirable performance in high temperature conditions.
Therefore, in some
embodiments, the quantity of the filler material (carbon black and/or silica)
is in the range
of about 10 phr to about 25 phr, and the quantity of peroxide curative is in
the range of
about 1 phr to about 6 phr. Such a combination results in advantageous
properties of
elongation greater than about 500% and permanent set less than about 25% at
room
temperature; elongation greater than about 450% and permanent set less than
about 25% at
130 degrees Celsius; and elongation greater than about 400% and permanent set
less than
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about 25% at 150 degrees Celsius. Additionally, such a combination results in
a cold
shrinkable material which does not tear while being held for seven days in a
200% radially
expanded state at 150 degrees Celsius.
Also, various embodiments of the cold shrinkable articles of the present
invention
exhibit chemical resistance to substances such as, for example, diesel fuel
and hydraulic
fluid. Some embodiments of the cold shrinkable articles of the present
invention exhibit a
percent weight increase of less than about 25% when immersed in diesel fuel at
about
49 C for 24 hours and/or a percent weight increase of less than about 10% when
immersed
in hydraulic fluid at about 71 C for 24 hours.
In reference to the Figures, a tubular cold shrinkable article 10 of the
present
invention is depicted in FIG. 1 in an initial relaxed state prior to any
expansion. The cold
shrinkable article 10 includes a radial wall 11, an inner surface 14, and an
outer surface 16.
When cold shrinkable article 10 is in the initial relaxed state, the radial
wall 11 has
a longitudinal length A, an inner diameter B, an outer diameter C, and a layer
thickness D.
The longitudinal length A and the inner diameter B may vary based upon
individual needs
of a given application, such as for example, the dimensions of a substrate
about which the
cold shrinkable article 10 will be placed. The outer diameter C is generally
determined by
the inner diameter B and the layer thickness D, where the layer thickness D is
ordinarily
substantially uniform both around a circumference E and along the length A of
the cold
shrinkable article 10. The layer thickness D is desirably thin enough to allow
the cold
shrinkable article 10 to readily expand from the initial relaxed state upon
application of
expansion forces.
Examples of suitable layer thickness D range from as low as about 0.060 inches
to
as high as about 0.25 inches. Examples of suitable inner diameter B range from
as low as
about 0.2 inches to as high as about 3 inches.
Various stages of a method for deploying the cold shrinkable article 10 are
depicted in FIGS. 2-5. The tubular cold shrinkable material 10 can be disposed
on a
removable core 18. The removable core 18 supports the cold shrinkable material
10 in an
expanded state. The cold shrinkable article 10 is depicted in an expanded
state on the
removable core 18 in FIG. 2. A substrate 20 is shown in FIG. 3 to be inserted
into the core
18, which supports the expanded form of the cold shrinkable article 10. The
cold
shrinkable article 10 partially deployed from the core 18 onto the substrate
20 is depicted
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in FIG. 4. The cold shrinkable article 10 fully deployed on the substrate 20
is depicted in
FIG. 5. The cold shrinkable article 10 may protect substrate 20 and/or may
identify the
substrate 20, which may, for example, comprise a wire, a cable, a fluid-
carrying pipe, or a
conduit.
To deploy the cold shrinkable article 10 on the substrate 20, the cold
shrinkable
article 10 is first cross-sectionally (or radially) expanded from the initial
relaxed state to
the expanded state and oriented on the core 18, as depicted in FIG. 2. As used
herein, the
terms "expanded", "expansion", "expanded state", and the like, refer to a
cross-sectional
expansion that increases inner diameter B and outer diameter C, as opposed to
a
io
longitudinal expansion that increases longitudinal length A, though such a
longitudinal
expansion is permissible. The cold shrinkable article 10 may be expanded and
placed onto
the core 18 in any conventional manner. The core 18 may generally have any
structure
that is suitable for retaining the cold shrinkable article 10 in the expanded
state. For
example, the core 18 may be a rigid, hollow, plastic tube.
When the cold shrinkable article 10 is in the expanded state, as best depicted
in
FIG. 2, the radial wall 11 has a longitudinal length A', an inner diameter B',
an outer
diameter C', and a wall thickness D'. Due to the expansion, the inner diameter
B' and the
outer diameter C' are larger than the inner diameter B and the outer diameter
C,
respectively. Suitable expansion of the cold shrinkable article 10 may
generally range
from about 150% to about 400%, where the expansion is characterized in terms
of the
percent expansion of the inner diameter B relative to the inner diameter B'.
Particularly
suitable expansion of the cold shrinkable article 10 may generally range from
about 200%
to about 300%.
The substrate 20 may be inserted within the core 18 holding the expanded form
of
the cold shrinkable article 10, as depicted in FIG. 3. In some embodiments,
the substrate
20 may be centered within the hollow portion of the core 18 using guide
fingers (not
shown) contained within the core 18. After the substrate 20 is inserted within
the core 18,
the cold shrinkable article 10 is conveyed from the core 18 onto the substrate
20, as
depicted in FIG. 4. The conveyance may be accomplished in a variety of
manners, such as
by sliding the cold shrinkable article 10 from the core 18 onto the substrate
20, or by
collapsing and removing the core 18 and thereby allowing the cold shrinkable
article 10 to
encompass and come into engagement with the substrate 20.
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When the cold shrinkable article 10 is removed from the core 18, the cold
shrinkable article 10 cold shrinkables from the expanded state toward (but not
necessarily
all the way to) the initial relaxed state. Whether or not the cold shrinkable
article 10
reaches the relaxed state depends on the diameter of the substrate 20. The
substrate 20
may have a diameter that allows the cold shrinkable article 10 to
substantially return to the
initial relaxed state and substantially regain the inner diameter B and the
outer diameter C,
as best depicted in FIG. 4. The inner diameter B of cold shrinkable article 10
in the initial
relaxed state may be slightly smaller than the exterior diameter of the
substrate 20, which
prevents the cold shrinkable article 10 from fully shrinking back to the
initial relaxed state,
1 o and thereby provides a snug and secure fit and engagement of the cold
shrinkable article
onto peripheral surfaces of the substrate 20. When the cold shrinkable article
10 is
fully deployed on the substrate 20, the inner surface 14 of the cold
shrinkable article 10
extends around, faces, and is typically in contact with the outer surface 22
of the substrate
20, as shown in FIG. 5.
In some embodiments, the outer surface 16 of the cold shrinkable article 10
may
include identifiers in the form of optional indicia 24, which may provide, for
example,
information relating to the cold shrinkable article 10 and/or the substrate
20. The indicia
24 may be a single mark or a plurality of marks, and may include a variety of
textual (i.e.,
alphanumeric) or graphical characters, symbols, and the like. The indicia 24
may also be
or include machine-readable indicia, such as bar codes. Also, the indicia 24
may have a
surface texture that is different from the texture of portions of the outer
surface 16 other
than the indicia 24.
The indicia 24 may be formed using any suitable process including, for
example,
ink application to the outer surface 16 and/or focused energy beam marking of
the outer
surface 16. A focused energy beam refers to a directionally focused stimulated
emission
of radiation, such as a laser beam, to produce a charring indicia on the
external surface of
the cold shrinkable material. The indicia 24, in the form of energy-beam
induced indicia,
may be formed, for example, by expanding the cold shrinkable article 10 from
the initial
relaxed state, marking the outer surface 16 by application of energy from a
focused energy
beam, and allowing the cold shrinkable article 10 to cold shrinkable back
toward the initial
relaxed state.
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To facilitate formation of energy-beam induced indicia, the elastomeric
compositions of the present invention may include an energy beam absorbent.
Such
energy beam absorbents, upon heating by a focused energy beam, may be employed
to
provide the indicia 24 with a different color than the color of the outer
surface 16 other
than the indicia. In this way, the color of the indicia 24 may contrast with
the color of the
outer surface 16 so the indicia are prominent and legible. If a high visual
legibility of the
indicia 24 is desired, both a pigment and an energy beam absorbent may be
included in the
elastomeric composition to provide a high contrast between the base color of
the outer
surface 16 and the contrasting color of the indicia 24. For further discussion
regarding
energy-beam induced identifiers and methods for marking cold shrinkable
articles, see
U.S. Publication No. US 2005-0214491 A1.
In some embodiments, indicia 24 are legible to an unaided eye of an individual
with 20/20 vision located at least about 36 centimeters away from indicia 24
when the cold
shrinkable article 10 is in an expanded state or a relaxed state.
Information pertaining to the cold shrinkable article 10 and/or the substrate
20 may
also be conveyed to a user by a base color of the outer surface 16 of the cold
shrinkable
article 10. For example, a blue base color of the outer surface 16 may convey
different
information to a user than a yellow or black base color. In some embodiments,
the cold
shrinkable article 10 may include both the indicia 24 and an information-
conveying base
color of the outer surface 16.
Cold shrinkable articles of the present invention may include a plurality of
elastomeric members. A branched cold shrinkable article 30 of the present
invention, in a
relaxed state prior to expansion, is depicted in FIG. 6. The cold shrinkable
article 30 may
include a plurality of hollow elastomeric portions (or members) 32A, 32B, 32C,
and 32D
that each have the inner surface 14 and the outer surface 16. The respective
inner surfaces
14 define elongate cavities (not shown) through each of the elastomeric
portions 32A,
32B, 32C, and 32D that are in communication with each other.
When the hollow elastomeric portions 32A, 32B, 32C, and 32D are stretched to
the
expanded state, cores 18 may be inserted within the expanded portions 32A,
32B, 32C,
and 32D, as depicted in FIG. 7, to maintain the portions 32A, 32B, 32C, and
32D in the
expanded state. The cold shrinkable article 30 (portions 32A, 32B, 32C, and
32D) may be
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deployed on one or more substrates 20 from the expanded states on the cores 18
pursuant
to the methods described above in relation to deployment of the cold
shrinkable article 10.
Cold shrinkable articles of the present invention may include corrugations
that
allow the cold shrinkable articles to exhibit a longitudinal length in a non-
corrugated
relaxed state that is substantially longer than the longitudinal length of the
cold shrinkable
articles when positioned on a removable core in an expanded, corrugated state.
A cold
shrinkable article 40, which is partially deployed from the core 18 onto the
outer surface
22 of the substrate 20, is depicted in FIG. 8. When in the expanded state on
the core 18,
the cold shrinkable article 40 includes a multitude of corrugations 42. As
illustrated by the
cold-shrunk portion 44, after release from the core 18, unsupported corrugated
portions of
the cold shrinkable article 40 extend longitudinally and the corrugations
formerly present
in the unsupported portions effectively disappear as the cold-shrunk portion
44 approaches
the initial relaxed state.
PROPERTY ANALYSIS AND CHARACTERIZATION PROCEDURES
Various analytical techniques may be used to characterize the properties of
cold
shrinkable articles of the present invention. Details about these analytical
techniques
follow. As used herein, "ASTM D412" refers to ASTM D412 ¨ 98a (Reapproved
2002)
entitled "Standard Test Methods for Vulcanized Rubber and Thermoplastic
Elastomers ¨
Tension", which was published in January 2003 and is available from the
American
Society for Testing and Materials International of West Conshohocken,
Pennsylvania.
I. Mechanical Property Tests
A. Elongation at Break and Stress at Break
Determinations of the stress at break and percent elongation at break for
dumbbells
formed from the elastomeric compositions of the present invention are
performed pursuant
to the procedures of Test Method A of ASTM D412 using a tensiTECH III tensile
tester
commercially available from Tech Pro of Cuyahoga Falls, Ohio.
A method described below similar to Test Method B of ASTM D412 may be used
to determine the elongation at break for ring samples cut from tubing formed
from
elastomeric compositions of the present invention. According to the method
employed
herein, ring samples, having a longitudinal width of about 3/8 of an inch, are
cut from the
tubing, and the ring samples are placed in a tensile testing apparatus. Each
end of each
ring sample is secured to a jaw between two 0.124 inch-diameter pins attached
to each
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jaw. The jaws of the tensile tester apparatus are then pulled in opposite
directions at a rate
of about 20 inches/minute and the strain and break loads are recorded. Unless
otherwise
stated herein, the elongation at break and stress at break tests are performed
in a
temperature-controlled box at a temperature of about 150 C, with the test
samples
conditioned for about 6 2 minutes at 150 C before conducting the tests.
The stress at break for the ring samples is computed using the following
equation:
Break Load
Actual Stress -.
(2 x Width of Ring Sample x Thickness of Ring Sample)
The elongation at break for the ring samples is computed using the following
equation:
Actual Elongation of ID at break = ((Stretched circumference - Initial
circumference)/(Initial circumference))x100.
B. Percent Permanent Set
The percent permanent set test illustrates the amount of elastic recovery an
article
exhibits. The percent permanent set is calculated using the following
equation:
100x(RelaxedLength - OriginalLength)
% PermanentS et -
(TestLength - OriginalLength)
To determine the percent permanent set for plaques, dumbbell test specimens
are
cut from plaques pursuant to the procedures of Test Method A of ASTM D-412.
Parallel
bench marks separated by a distance of an inch are placed at the approximate
center of
each dumbell. The dumbbells are placed in a set fixture and stretched until
the distance
between the bench marks equals 2 inches, which correlates to 100% strain. The
loaded set
fixture is then placed in a 100 C oven for 3 hours. After 3 hours, the
fixtures are removed
from the oven and the stretched dumbbells are allowed to cool at room
temperature (21 C
2 C) for 1 hour. The stretched dumbbells are removed from the set fixture and
placed on
a smooth wooden or cardboard surface. The distance between the parallel bench
marks is
measured after waiting 30 2 minutes. The percent permanent set is determined
using the
formula provided above with the original length equaling 1 inch, the test
length equaling 2
inches, and the relaxed length equaling the final distance between the bench
marks after
cooling.
To determine the percent permanent set for tubing, ring samples having a
length of
3/8 of an inch are cut from the tubing and the initial diameters of the ring
samples are
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measured. The ring samples are then inserted over a steel mandrel having a
diameter about
twice the internal diameter of the tubing ring samples, which causes the ring
samples to
radially stretch about 100% in diameter. An end of the mandrel is equipped
with a conical
shape to facilitate inserting & removing the mandrel from the ring samples.
While
stretched on the mandrel, the ring samples are placed in a 100 C oven for 3
hours. After
expiration of the 3-hour period, the mandrel and stretched ring samples are
removed from
the oven and allowed to cool at room temperature (21 C 2 C ) for 1 hour. The
ring
samples are then removed from the mandrel and placed on a smooth wooden or
cardboard
surface. The internal diameters of the ring samples are measured after passage
of 30 2
io minutes, and the following formula is used to compute the percent
permanent set of the
ring samples:
% Permanent Set = 100 (rd-od),
md-od
where rd is the relaxed diameter, od is the original diameter, and md is the
mandrel
diameter.
C. Tubing Split Test
Tubing split tests are conducted to illustrate the tear properties of the cold
shrinkable articles over time. The test is conducted using tubing samples
prepared from
elastomeric compositions of the present invention pursuant to the methods
described
above. Samples of tubing having a length of about 3 to 4 inches are cut and
placed over
steel mandrels, which have a diameter about three times the internal diameter
of the tubing
samples. As such, the tubing samples are expanded radially by about 200%.
While
retained in a state of about 200% radial expansion, the samples are placed in
a 150 C oven
for seven days. After expiration of the seven-day period, the elongated
samples are
visually inspected for signs of tearing. Tubing samples are deemed to have
failed the split
test if any tearing or splitting is visually observed by an unaided human eye.
II. Fluid Resistance Tests
The fluid resistance of cold shrinkable articles of the present invention is
determined by cutting dumbbell test specimens (pursuant to the methods of Test
Method A
of ASTM D412) from plaques formed from compositions of the present invention.
The
test specimens are weighed individually and then immersed in either hydraulic
fluid or
diesel fuel in wide test tubes. The test tubes containing the diesel fuel are
placed in an oil
bath maintained at a temperature of about 49 C for 24 hours and the test tubes
containing
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the hydraulic fluid were placed in an oil bath maintained at a temperature of
about 71 C
for 24 hours. The test specimens are then removed from test tubes, padded dry
with filter
paper, and weighed individually. The respective percent absorptions of diesel
fuel and
hydraulic fluid for the test specimens are then computed using the initial
weights and the
final weights of the dumbbell test specimens.
III. Laser Marking Test
The visual legibility of the indicia is qualitatively determined for cold
shrinkable
articles pursuant to the following procedure. Tubing without indicia, having a
1.0 mm
outer diameter, is expanded onto a core with a 2.0 cm diameter. The expanded
tubing is
then laser marked to form indicia by a Nd:YAG laser system. The Nd:YAG laser
system
is commercially availably under the trade name "Hi-Mark" No. 400 from GSI
Lumonics,
Inc. of Kanata, Ontario, Canada. The laser settings for the Nd:YAG laser
system include a
power setting of 64.8 watts, a rate of marking 5.1 cm/minute, and a frequency
of 6 wave
peaks per second. The set distance of the laser system head to the outer
surface of the
tubing is 18.3 cm (7.2 inches). The indicia is marked so the indicia, with the
tubing in the
expanded state, exhibits a type-face height in a circumferential direction
about the tubing
of 2.0 mm.
After marking, the tubing is removed from the core and allowed to
substantially
cold shrinkable back toward the relaxed state. The indicia on the tubing
substantially in
the relaxed state is then visually observed by an unaided human eye. The
marking is
determined to be acceptable if the indicia (exhibiting a type-face height of
2.0 mm) on the
tubing is visually legible by an unaided human eye (i.e., about 20/20 vision)
from a
distance of at least about 36 cm (about 14 inches).
EXAMPLES
The present invention is more particularly described in the following
examples that are intended as illustrations only, since numerous modifications
and
variations within the scope of the present invention will be apparent to those
skilled in the
art. Unless otherwise noted, all parts, percentages, and ratios reported in
the following
examples are on a weight basis, and all reagents used in the examples were
obtained, or
are available, from general chemical suppliers such as the Sigma-Aldrich
Chemical
Company of Saint Louis, Missouri, or may be synthesized by conventional
techniques.
Also, unless otherwise stated, all performance data included herein for tubing
is for tubing
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cured in an oxygen-free atmosphere. In addition, unless otherwise noted, all
tests were
performed pursuant to the property analysis and characterization procedures
described
above.
The following compositional abbreviations are used in the following
Examples:
DAIKIN G-801: A fluoroelastomer copolymer of vinylidene fluoride
and
hexafluoropropylene commercially available from Daikin
Industries of Osaka, Japan.
DAIKIN G-802: A fluoroelastomer copolymer of vinylidene fluoride and
hexafluoropropylene commercially available from Daikin
Industries of Osaka, Japan.
AEROSIL R974: A silane-treated, fumed silica commercially
available from
Degussa Company of Parsippany, NJ.
N-110 Black: A reinforcement-grade carbon black commercially available
from Cabot Corporation, Billerica, MA.
N-990 Black: A non-reinforcement-grade carbon black commercially
available from Cabot Corporation, Billerica, MA.
TAIC DLC-A: A cross-linking co-agent commercially available
from
Natrochem, Inc. of Savannah, GA.
Zinc Omadine: A fungicide solution of 65% 2-pyridinethio1-1-
oxide, zinc
complex in a paraffinic oil (i.e., Zinc Omadine), commercially
available from Arch Chemicals, Inc. of Cheshire, Connecticut.
VAROX DBPH-50-HP: A 2,5-dimethy1-2,5-di(t-butylperoxy)hexane cross-
linking agent
peroxide curative commercially available from R.T. Vanderbilt
Company of Norwalk, CT.
The Examples concern cold shrinkable articles of the present invention in the
form
of tubing and plaques. The component concentrations of the elastomeric
compositions
used to form the cold shrinkable articles of the Examples are provided in
Table 2. The
elastomeric compositions of the Examples were prepared by combining the
components
provided in Table 2 in a first mixing step, and then mixing these components
in a
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Banburry mixer at between about 20 and 40 revolution-per-minute for about 20
minutes at
a temperature of about 60 C. The compositions were then further mixed in a 2-
roll mixing
mill heated to about 50 C for about 5 minutes. The TAIC DLC-A listed in Table
2 was
then added to each composition in a second mixing step and the compositions
were mixed
for an additional 5 minutes. The compositions were then sheeted out in
conventional
fashion and cooled to the ambient temperature (22-24 C).
TABLE 2
Components (phr) BT 7 BT 17 BT 18 LMC LTC
(Control) (Control)
Daikin G-801 100 0 0 0 100
Daikin G-802 0 100 100 100 0
Aerosil R974 5 5 10 0 0
N-110 Black 10 10 5 0 0
N-990 Black 0 0 0 10 10
Zinc Oxide 2 2 2 2 2
Zinc Omadine Paste 0.75 0.75 0.75 0.75 0.75
TAIC DLCA 4.2 4.2 4.2 4.2 4.2
Varox DBPH-50HP 2.5 2.5 2.5 2.5 2.5
The elastomeric compositions of the Examples were extruded into tubing having
an internal diameter of about 0.25 inches and a wall thickness of about 0.18
cm using a 3/4
inch extruder with a L/D ratio of 20. The extrusions were done at a barrel
temperature of
about 60 C and a die temperature between about 30 C and 60 C. The resulting
tubing was
cured by peroxide curing. The percent elongation at break and percent
permanent set at
room temperature, 130C, and 150C were determined. Also, the split resistance
at 150 C
for 7 days, stress at break at 150 C was also determined. The results of these
tests are
included in Tables 2 and 3.
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TABLE 3
Compound BT 7 BT 17 BT 18
100% 449 451 450
200% 791 796 768
300% 1238 1227 1179
Tensile (psi) 3219 3068 3033
Elongation-at-break 618 606 619
(-'q Room Temp
Permanent Set (%) 23.3 23.4 22.8
TABLE 4
Permanen Permanen Elongatio Elongation
Composition
t Set @ t Set @ n @ 130C @ 150C
130C (%) 150C (%) (%) (%)
LMC n/a n/a 258 214
(Control)
LTC (Control) n/a n/a 272 242
BT 7 23.4 23.2 513 417
BT 17 23.3 23.5 514 423
BT 18 22.6 22.9 468 400
Table 3 provides data at room temperature, and Table 4 provides data at
elevated
temperatures. The data provided in Tables 2 and 3 illustrates the expansion
capabilities,
durability, and tear performance at elevated temperatures of cold shrinkable
articles
formed from the elastomeric compositions of the Examples. The tubing samples
of the
Examples each exhibited a percent permanent set of less than 25%. In addition,
all tubing
samples formed from each of the compositions in BT 7, BT 17, and BT 18 passed
the
extended split test provided in the Property Analysis and Characterization
Procedures
scction of this documcnt.
In addition, the tubing samples of the Examples all marked well with a YAG
laser
and passed the laser marking test, when tested pursuant to the laser-marking
procedures
including in the Property Analysis and Characterization Procedures section of
this
document.
The scope of the claims should not be limited by the preferred embodiments
described
herein, but should be given the broadest interpretation consistent with the
invention as a whole.
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